Transcript
MIC2950/2951
Micrel
MIC2950/2951 150mA Low-Dropout Voltage Regulator
General Description The MIC2950 and MIC2951 are “bulletproof” micropower voltage regulators with very low dropout voltage (typically 40mV at light loads and 250mV at 100mA), and very low quiescent current. Like their predecessors, the LP2950 and LP2951, the quiescent current of the MIC2950/MIC2951 increases only slightly in dropout, thus prolonging battery life. The MIC2950/MIC2951 are pin for pin compatible with the LP2950/LP2951, but offer lower dropout, lower quiescent current, reverse battery, and automotive load dump protection. The key additional features and protection offered include higher output current (150mA), positive transient protection for up to 60V (load dump), and the ability to survive an unregulated input voltage transient of –20V below ground (reverse battery). The plastic DIP and SOIC versions offer additional system functions such as programmable output voltage and logic controlled shutdown. The 3-pin TO-92 MIC2950 is pincompatible with the older 5V regulators. These system functions also include an error flag output that warns of a low output voltage, which is often due to failing batteries on the input. This may also be used as a power-on reset. A logic-compatible shutdown input is also available which enables the regulator to be switched on and off. This part may also be pin-strapped for a 5 V output, or programmed from 1.24 V to 29 V with the use of two external resistors.
Features • • • • • • • • • • • •
High accuracy 3.3, 4.85, or 5V, guaranteed 150mA output Extremely low quiescent current Low-dropout voltage Extremely tight load and line regulation Very low temperature coefficient Use as regulator or reference Needs only 1.5µF for stability Current and thermal limiting Unregulated DC input can withstand –20V reverse battery and +60V positive transients Error flag warns of output dropout (MIC2951) Logic-controlled electronic shutdown (MIC2951) Output programmable from 1.24V to 29V (MIC2951)
Applications • • • • • • •
Automotive Electronics Battery Powered Equipment Cellular Telephones SMPS Post-Regulator Voltage Reference Avionics High Efficiency Linear Power Supplies
Block Diagram
Unregulated DC Supply
FB
IN OUT SNS
Error Amp. 182k SHDN
TTL/CMOS Control Logic Input
60mV
60k Error Detection Comparator
TAP
330k
TTL/CMOS Compatible Error Output
ERR 1.5µF
1.23V REF.
GND
MIC2951-0x
February 1999
5V/150mA Output
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MIC2950/2951
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The MIC2950 is available as either an -05 or -06 version. The -05 and -06 versions are guaranteed for junction temperatures from –40°C to +125°C; the -05 version has a tighter output and reference voltage specification range over temperature. The MIC2951 is available as an -02 or -03 version.
The MIC2950 and MIC2951 have a tight initial tolerance (0.5% typical), a very low output voltage temperature coefficient which allows use as a low-power voltage reference, and extremely good load and line regulation (0.04% typical). This greatly reduces the error in the overall circuit, and is the result of careful design techniques and process control.
Ordering Information Part Number
Voltage
Accuracy Temperature Range*
Package
MIC2950-05BZ
5.0V
0.5%
–40°C to +125°C
TO-92
MIC2950-06BZ
5.0V
1.0%
–40°C to +125°C
TO-92
MIC2951-02BM
5.0V
0.5%
–40°C to +125°C
8-pin SOIC
MIC2951-03BM
5.0V
1.0%
–40°C to +125°C
8-pin SOIC
MIC2951-02BN
5.0V
0.5%
–40°C to +125°C
8-pin plastic DIP
MIC2951-03BN
5.0V
1.0%
–40°C to +125°C
8-pin plastic DIP
MIC2951-03BMM
5.0V
1.0%
–40°C to +125°C
8-lead MM8™
MIC2951-3.3BM
3.3V
1.0%
–40°C to +125°C
8-pin SOIC
MIC2951-4.8BM
4.85V
1.0%
–40°C to +125°C
8-pin SOIC
* junction temperature
Pin Configuration MIC2951-xx MIC2950-xx 3
2
1
OUT
IN
OUT 1
8
IN
SNS 2
7
FB
SHDN 3
6
TAP
GND 4
5
ERR
GND
TO-92 (Z) (Bottom View)
DIP (N), SOIC (M), MM8™ (MM) (Top View)
Pin Description Pin # MIC2950
Pin # MIC2951
Pin Name
3
1
OUT
Regulated Output
2
SNS
Sense (Input): Output-voltage sensing end of internal voltage divider for fixed 5V operation. Not used in adjustable configuration.
3
SHDN
4
GND
Ground
5
ERR
Error Flag (Output): Active low, open-collector output (low = error, floating = normal).
6
TAP
3.3V/4.85/5V Tap: Output of internal voltage divider when the regulator is configured for fixed operation. Not used in adjustable configuration.
7
FB
Feedback (Input): 1.235V feedback from internal voltage divider’s TAP (for fixed operation) or external resistor network (adjustable configuration).
8
IN
Unregulated Supply Input
2
1
Pin Function
Shutdown/Enable (Input): TTL compatible input. High = shutdown, low or open = enable.
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Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Input Suppy Voltage (VIN) Note 5 ................. –20V to +60V Feedback Input Voltage (VFB) Note 6, 7 ...... –1.5V to +26V Shutdown Input Voltage (VSHDN) Note 6 ..... –0.3V to +30V Power Dissipation (PD) Note 4 ................ Internally Limited Storage Temperature .............................. –65°C to + 150°C Lead Temperature (soldering, 5 sec.) ....................... 260°C ESD, Note 3
Input Supply Voltage (VIN) ........................... +2.0V to +30V Junction Temperature (TJ) ....................................... Note 4 MIC2950-05/MIC2950-06 ..................... –40°C to +125°C MIC2951-02/MIC2950-03 ..................... –40°C to +125°C
Electrical Characteristics VIN = 6V; IL = 100µA; CL = 1µF; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; Note 8; unless noted. Parameter
Condition
Output Voltage
Output Voltage
Output Voltage Over Full Temperature Range
Output Voltage Over Load Variation
Output Voltage Temperature Coefficient
Line Regulation
February 1999
Min
Typ
Max
Units
MIC295x-02/-05 (±0.5%), TJ = 25°C
4.975
5.000
5.025
V
MIC295x-03/-06 (±1%), TJ = 25°C
4.950
5.000
5.050
V
MIC2951-3.3 (±1%), TJ = 25°C
3.267
3.300
3.333
V
MIC2951-4.8 (±1%), TJ = 25°C
4.802
4.850
4.899
V
MIC295x-02/-05 (±0.5%), –25°C ≤ TJ ≤ +85°C
4.950
5.050
V
MIC295x-03/-06 (±1%), –25°C ≤ TJ ≤ +85°C
4.925
5.075
V
MIC2951-3.3 (±1%), –25°C ≤ TJ ≤ +85°C
3.251
3.350
V
MIC2951-4.8 (±1%), –25°C ≤ TJ ≤ +85°C
4.777
4.872
V
MIC295x-02/-05 (±0.5%), –40°C to +125°C
4.940
5.060
V
MIC295x-03/-06 (±1%), –40°C to +125°C
4.900
5.100
V
MIC2951-3.3 (±1%), –40°C to +125°C
3.234
3.366
V
MIC2951-4.8 (±1%), –40°C to +125°C
4.753
4.947
V
MIC295x-02/-05 (±0.5%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
4.930
5.070
V
MIC295x-03/-06 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
4.880
5.120
V
MIC2951-3.3 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
3.221
3.379
V
MIC2951-4.8 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ TJ(max)
4.733
4.967
V
MIC295x-02/-05 (±0.5%), Note 9
20
100
ppm/°C
MIC295x-03/-06 (±1%), Note 9
50
150
ppm/°C
MIC2951-3.3 (±1%), Note 9
50
150
ppm/°C
MIC2951-4.8 (±1%), Note 9
50
150
ppm/°C
MIC295x-02/-05 (±0.5%), Note 10, 11
0.03
0.10 0.20
% %
MIC295x-03/-06 (±1%), Note 10, 11
0.04
0.20 0.40
% %
MIC2951-3.3 (±1%), Note 10, 11
0.04
0.20 0.40
% %
MIC2951-4.8 (±1%), Note 10, 11
0.04
0.20 0.40
% %
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Parameter
Condition
Load Regulation
Dropout Voltage
Ground Current
Dropout Ground Current
Min
Typ
Max
Units
MIC295x-02/-05 (±0.5%), 100µA ≤ IL ≤ 150mA, Note 10
0.04
0.10 0.20
% %
MIC295x-03/-06 (±1%), 100µA ≤ IL ≤ 150mA, Note 10
0.10
0.20 0.30
% %
MIC2951-3.3 (±1%), 100µA ≤ IL ≤ 150mA, Note 10
0.10
0.20 0.30
% %
MIC2951-4.8 (±1%), 100µA ≤ IL ≤ 150mA, Note 10
0.10
0.20 0.30
% %
MIC295x-02/-03/-05/-06, IL = 100µA, Note 12
40
80 140
mV mV
MIC295x-02/-03/-05/-06, IL = 100mA, Note 12
250
300
mV
MIC295x-02/-03/-05/-06, IL = 150mA, Note 12
300
450 600
mV mV
MIC2951-3.3 (±1%), IL = 100µA, Note 12
40
80 150
mV mV
MIC2951-3.3 (±1%), IL = 100mA, Note 12
250
350
mV
MIC2951-3.3 (±1%), IL = 150mA, Note 12
320
450 600
mV mV
MIC2951-4.8 (±1%), IL = 100µA, Note 12
40
80 140
mV mV
MIC2951-4.8 (±1%), IL = 100mA, Note 12
250
300
mV
MIC2951-4.8 (±1%), IL = 150mA, Note 12
300
450 600
mV mV
MIC295x-02/-03/-05/-06, IL = 100µA
120
180 300
µA µA
MIC295x-02/-03/-05/-06, IL = 100mA
1.7
2.5 3.5
mA mA
MIC295x-02/-03/-05/-06, IL = 150mA
4
6 8
mA mA
MIC2951-3.3 (±1%), IL = 100µA
100
180 300
µA µA
MIC2951-3.3 (±1%), IL = 100mA
1.7
2.5
mA
MIC2951-3.3 (±1%), IL = 150mA
4
6 10
mA mA
MIC2951-4.8 (±1%), IL = 100µA
120
180 300
µA µA
MIC2951-4.8 (±1%), IL = 100mA
1.7
2.5 3.5
mA mA
MIC2951-4.8 (±1%), IL = 150mA
4
6 8
mA mA
MIC295x-02/-03/-05/-06 (±0.5%), VIN = 4.5V, IL = 100µA
280
350 400
µA µA
MIC2951-3.3 (±1%), VIN = 3.0V, IL = 100µA
150
350 400
µA µA
MIC2951-4.8 (±1%), VIN = 4.3V, IL = 100µA
280
350 400
µA µA
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Parameter
Condition
Current Limit
Typ
Max
Units
VOUT = 0V
300
400 450
mA mA
Thermal Regulation
Note 13
0.05
0.20
%/W
Output Noise
10Hz to 100kHz, CL = 1.5µF
430
µVRMS
10Hz to 100kHz, CL = 200µF
160
µVRMS
10Hz to 100kHz, CL = 3.3µF, 0.01µF bypass Feedback to Output
100
µVRMS
Reference Voltage
Reference Voltage
Min
MIC295x-02/-05 (±0.5%)
1.220 1.200
1.235
1.250 1.260
V V
MIC295x-03/-06 (±1%)
1.210 1.200
1.235
1.260 1.270
V V
MIC2951-3.3 (±1%)
1.210 1.200
1.235
1.260 1.270
V V
MIC2951-4.8 (±1%)
1.210 1.200
1.235
1.260 1.270
V V
MIC295x-02/-05 (±0.5%), Note 14
1.190
1.270
V
MIC295x-03/-06 (±1%), Note 14
1.185
1.285
V
MIC2951-3.3 (±1%), Note 14
1.185
1.285
V
MIC2951-4.8 (±1%), Note 14
1.185
1.285
V
40 60
nA nA
Feedback Bias Current Reference Voltage Temperature Coefficient
20 MIC295x-02/-05 (±0.5%), Note 9
20
ppm/°C
MIC295x-03/-06 (±1%), Note 9
50
ppm/°C
MIC2951-3.3 (±1%), Note 9
50
ppm/°C
MIC2951-4.8 (±1%), Note 9
50
ppm/°C
0.1
nA/°C
Feedback Bias Current Temperature Coefficient Error Comparator (Flag) Output Leakage Current
VOH = 30V
0.01
1.00 2.00
µA µA
Error Comparator (Flag) Output Low Voltage
VIN = 4.5V, IOL = 200µA
150
250 400
mV mV
Error Comparator Upper Threshold Voltage
Note 15
Error Comparator Lower Threshold Voltage
Note 15
75
Error Comparator Hysteresis
Note 15
15
February 1999
40 25
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mV mV 95 140
mV mV mV
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MIC2950/2951
Micrel
Parameter
Condition
Shutdown Input Logic Voltage
MIC295x-02/-05 (±0.5%) Low High
Min
Units
0.7
V V V
0.7
V V V
0.7
V V V
0.7
V V V
2.0 1.3 2.0
MIC2951-3.3 (±1%) Low High
1.3 2.0
MIC2951-4.8 (±1%) Low High
Regulator Output Current in Shutdown
Max
1.3
MIC295x-03/-06 (±1%) Low High
Shutdown Input Current
Typ
1.3 2.0
VSHUTDOWN = 2.4V
30
50 100
µA µA
VSHUTDOWN = 30V
450
600 750
µA µA
3
10 20
µA µA
Note 7
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions are recommended.
Note 4.
The junction-to-ambient thermal resistance of the TO-92 package is 180°C/W with 0.4” leads and 160°C/W with 0.25” leads to a PC board. The thermal resistance of the 8-pin DIP package is 105°C/W junction-to-ambient when soldered directly to a PC board. Junction-to-ambient thermal resistance for the SOIC (M) package is 160°C/W. Junction-to-ambient thermal resistance for the MM8™ (MM) is 250°C/W.
Note 5.
The maximum positive supply voltage of 60V must be of limited duration (≤100ms) and duty cycle (≤1%). The maximum continuous supply voltage is 30V.
Note 6.
When used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage should be diodeclamped to ground.
Note 7.
VSHDN ≥ 2V, VIN ≤ 30 V, VOUT = 0, with the FB pin connected to TAP.
Note 8.
Additional conditions for 8-pin devices are VFB = 5V, TAP and OUT connected to SNS (VOUT = 5V) and VSHDN ≤ 0.8V.
Note 9.
Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 10. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are covered in the specification for thermal regulation. Note 11. Line regulation for the MIC2951 is tested at 150°C for IL = 1mA. For IL = 100µA and TJ = 125°C, line regulation is guaranteed by design to 0.2%. See Typical Performance Characteristics for line regulation versus temperature and load current. Note 12. Dropout voltage is defined as the input to output differential at which the output voltage drops 100mV below its nominal value measured at 1V differential. At very low values of programmed output voltage, the minimum input supply voltage of 2V (2.3V over temperature) must be taken into account. Note 13. Thermal regulation is defined as the change in output voltage at a time “t” after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 50mA load pulse at VIN = 30V (1.25W pulse) for t = 10ms. Note 14. VREF ≤ VOUT ≤ (VIN – 1 V), 2.3V ≤ VIN ≤ 30V, 100µA < IL ≤ 150mA, TJ ≤ TJMAX. Note 15. Comparator thresholds are expressed in terms of a voltage differential at the FB terminal below the nominal reference voltage measured at 6V input. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = VOUT /VREF = (R1 + R2)/R2. For example, at a programmed output voltage of 5V, the error output is guaranteed to go low when the output drops by 95mV x 5V/1.235V = 384mV. Thresholds remain constant as a percent of VOUT as VOUT is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
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Typical Characteristics Ground Pin Current
Dropout Characteristics
0.1
0.01 0.1
5 4
1 0
1
10
150
1
2
3
4
5
5
6 7
50
150 100 50
5.0 4.98 0.2%
4.96
6 VIN = 6V IL = 150 mA 5
4 -75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
Short Circuit Current
200 150 100 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (°C)
60 40 20 1
2
3
4
5
6
7
8
INPUT VOLTAGE (V)
Ground Pin Current 9
7
5 IL = 150 mA 3
0 0
1
2
3
4
5
6
7
8
INPUT VOLTAGE (V)
Dropout Voltage 500
IL = 150 mA
500 400 300 100
IL = 100 µA
50
0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (°C)
3-55
DROPOUT VOLTAGE (mV)
250
3
IL = 0
80
Dropout Voltage DROPOUT VOLTAGE (mV)
300
100
0
600
350
IL = 1 mA
120
0
7
0 -75 -50 -25 0 25 50 75 100 125 150
400
140
Ground Pin Current
450
5 6 7 8 9 10
Ground Pin Current
TEMPERATURE (°C)
QUIESCENT CURRENT (mA)
VIN = 6V IL = 100 µA
200
February 1999
100
INPUT VOLTAGE (V)
QUIESCENT CURRENT (µA)
5.02
Ground Pin Current 300
RL = ∞
150
180
5.04
INPUT VOLTAGE (V)
250
200
0 1 2 3 4
4.94 -75 -50 -25 0 25 50 75 100 125 150
8 9 10
350
R L = 50k Ω
250
INPUT VOLTAGE (V)
QUIESCENT CURRENT (mA)
2 3 4
300
6
5.06
0 1
350
Output Voltage vs. Temperature of 3 Representative Units R L = 50Ω
Input Current
0 0
OUTPUT VOLTAGE (V)
INPUT CURRENT (mA)
R L = 33 Ω
2
Input Current
QUIESCENT CURRENT (µA)
R L = 50kΩ
3
LOAD CURRENT (mA)
SHORT CIRCUIT CURRENT (mA)
INPUT CURRENT (µA)
1
160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0
400
6 OUTPUT VOLTAGE (V)
QUIESCENT CURRENT
10
400 300 200
TJ = 25 °C
100 0
150 0.1
1
10
100
OUTPUT CURRENT (mA)
MIC2951 Minimum Operating Voltage
20
2.0 1.9 1.8 1.7 1.6 -75 -50 -25 0 25 50 75 100 125 150
10 0 -10 -20 -30 -75 -50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
4 HYSTERESIS 2 0 PULLUP RESISTOR TO SEPARATE 5V SUPPLY
1
2
3
4
5
1.5 1.0
TA = -55°C 0.5
4
6
8
10
OUTPUT VOLTAGE CHANGE (mV)
2
80 60 40 20 0 -20 -40 -60
LOAD CURRENT
0
TA = 25°C
0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
6
C L = 4.7 µF VOUT = 5V
100 mA 100 µA
TA = 125°C
2.0
Load Transient Response 125 100 75 50 25 0 -25 -50
100 mA 100 µA
I0 = 100 mA
0.5 VOUT = 5V C L = 4.7 µF
0.05 0.02 0.01
10
100
1K
10K 100K 1M
FREQUENCY (Hz)
-150 TA = 25°C -200 TA = –55°C -250 -2.0 -1.5 -1.0 -0.5 0
-50 mV
C L = 4.7µF IL = 1 mA VOUT = 5V
8V 6V 4V 200
C L = 15 µF VOUT = 5V
12
16
20
7 6 5 4 3 2 1 0 2 0 -2
IL = 10 mA VIN = 8V CL = 10 µF VOUT = 5V
-100 0 100 200 300 400 500 600 700
Ripple Rejection 90
70
IL = 0
60 50
20
800
TIME (µS)
80
40
600
CL = 1.5 µF
Ripple Rejection
30
400
MIC2951 Enable Transient
8
1.0
0
Load Transient Response
4
0.5
Line Transient Response
400 mV 200 mV
TIME (mS)
RIPPLE REJECTION (dB)
OUTPUT IMPEDANCE (OHMS)
I0 = 1 mA
0.2 0.1
-100
0
90
I0 = 100 µA
2 1
TA = 125°C
TIME (µS)
0
Output Impedance 5
-50
OUTPUT LOW VOLTAGE (V)
TIME (mS)
10
OUTPUT VOLTAGE CHANGE
VOUT = 5V
INPUT VOLTAGE (V)
OUTPUT VOLTAGE LOAD CHANGE (mV) CURRENT
MIC2951 Comparator Sink Current
INPUT VOLTAGE
2.5
6
0
PIN 7 DRIVEN BY EXTERNAL SOURCE (REGULATOR RUN OPEN LOOP)
0
FEEDBACK VOLTAGE (V)
SHUTDOWN OUTPUT PIN VOLTAGE (V) VOLTAGE (V)
MIC2951 Error Comparator Output
-2
MIC2951 Feedback Pin Current
TEMPERATURE (°C)
SINK CURRENT (mA)
COMPARATOR OUTPUT (V)
8
50 FEEDBACK CURRENT (µA)
2.1
MIC2951 Feedback Bias Current
RIPPLE REJECTION (dB)
2.2
Micrel
BIAS CURRENT (nA)
MINIMUM OPERATING VOLTAGE (V)
MIC2950/2951
CL = 1.5 µF VIN = 6V VOUT = 5V 101
10 2
10 3
IL = 100 µA
10 4
10
FREQUENCY (Hz)
3-56
106
80
CL = 1.5 µF VIN = 6V VOUT = 5V
70 I = 1 mA L 60 50 40 30 20 101
IL = 10 mA 102
10 3
10 4
10 5
106
FREQUENCY (Hz)
February 1999
Ripple Rejection VOLTAGE NOISE SPECTRAL DENSITY (µV/√ Hz)
IL = 50 µA
60
IL = 100 mA
50 40
CL = 1.5 µF 30 VIN = 6V VOUT = 5V 20 10
101
102
10 3
10 4
10 5
Output Noise IL = 100 mA
3.0
CL = 4.7 µF
2.5
CL = 220 µF
2.0 CL = 3.3 µF
1.5 1.0
0.01 µF BYPASS PIN 1 TO PIN 7
0.5
0.0 102
106
1.8 1.6 1.4 1.2 1.0 0.8 0.6 -75 -50 -25 0 25 50 75 100 125 150
OUTPUT VOLTAGE CHANGE (mV)
SHUTDOWN THRESHOLD VOLTAGE (V)
Shutdown Threshold Voltage
TJ
100 80
MAX
= 125°C
TA = 25°C
60 40
T = 85°C
20
A
0 0
5
10
15
20
25
INPUT VOLTAGE (V)
February 1999
30
POWER OUTPUT VOLTAGE DISSIPATION (W) CHANGE (mV)
OUTPUT CURRENT (mA)
TO-92 PACKAGE .25" LEADS SOLDERED TO PC BOARD
120
200
100
0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (°C)
MIC2951 Maximum Rated Output Current
30 25 20 15 T = 150°C 10 J 5 0 10 5 TJ = 125°C 0 -5 -10 5 10 15
150 IL = 100 µA IL = 1 mA
IL = 100 µA
8-PIN SOIC SOLDERED TO PC BOARD
140
TJ
130
= 125°C
VOUT = 5V TA = 25°C
100 80 60 TA = 50°C 40 TA = 85°C 20 0
20
25
30
0
Thermal Response
600
5 4 2 0 -2 1
MAX
120
INPUT VOLTAGE (V)
MIC2950 Maximum Rated Output
130
10 5
300
Line Regulation
TEMPERATURE (°C)
140
10 4
MIC2951 Divider Resistance 400
FREQUENCY (Hz)
FREQUENCY (Hz)
150
10 3
OUTPUT CURRENT (mA)
70
3.5
OUTPUT CURRENT (mA)
RIPPLE REJECTION (dB)
80
Micrel
PIN 2 TO PIN 4 RESISTANCE (kΩ )
MIC2950/2951
1.25W
5 10 15 20 25 INPUT VOLTAGE (V)
30
Fold-Back Current Limiting
500 400 300 200
0 -1
100 0
10
20
30
TIME (µS)
3-57
40
50
0
1
2
3
4
OUTPUT VOLTAGE (V)
5
3
MIC2950/2951
Micrel
Applications Information Automotive Applications The MIC2950/2951 are ideally suited for automotive applications for a variety of reasons. They will operate over a wide range of input voltages, have very low dropout voltages (40mV at light loads), and very low quiescent currents. These features are necessary for use in battery powered systems, such as automobiles. They are also “bulletproof” devices; with the ability to survive both reverse battery (negative transients up to 20V below ground), and load dump (positive transients up to 60V) conditions. A wide operating temperature range with low temperature coefficients is yet another reason to use these versatile regulators in automotive designs.
External Capacitors A 1.5 µF (or greater) capacitor is required between the MIC2950/MIC2951 output and ground to prevent oscillations due to instability. Most types of tantalum or aluminum electrolytics will be adequate; film types will work, but are costly and therefore not recommended. Many aluminum electrolytics have electrolytes that freeze at about –30°C, so solid tantalums are recommended for operation below –25°C. The important parameters of the capacitor are an effective series resistance of about 5Ω or less and a resonant frequency above 500kHz. The value of this capacitor may be increased without limit. At lower values of output current, less output capacitance is required for output stability. The capacitor can be reduced to 0.5µF for current below 10mA or 0.15µF for currents below 1 mA. Using the 8-pin versions at voltages below 5V runs the error amplifier at lower gains so that more output capacitance is needed. For the worst-case situation of a 150mA load at 1.23V output (Output shorted to Feedback) a 5µF (or greater) capacitor should be used. The MIC2950 will remain stable and in regulation with no load in addition to the internal voltage divider, unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive applications. When setting the output voltage of the MIC2951 version with external resistors, a minimum load of 1µA is recommended. A 0.1µF capacitor should be placed from the MIC2950/ MIC2951 input to ground if there is more than 10 inches of wire between the input and the AC filter capacitor or if a battery is used as the input. Stray capacitance to the MIC2951 Feedback terminal (pin 7) can cause instability. This may especially be a problem when using high value external resistors to set the output voltage. Adding a 100pF capacitor between Output and Feedback and increasing the output capacitor to at least 3.3µF will remedy this.
Error Detection Comparator Output A logic low output will be produced by the comparator whenever the MIC2951 output falls out of regulation by more than approximately 5%. This figure is the comparator’s built-in
offset of about 60mV divided by the 1.235V reference voltage. (Refer to the block diagram on Page 1). This trip level remains “5% below normal” regardless of the programmed output voltage of the MIC2951. For example, the error flag trip level is typically 4.75V for a 5V output or 11.4V for a 12V output. The out of regulation condition may be due either to low input voltage, current limiting, thermal limiting, or overvoltage on input (over ≅ 40V). Figure 1 is a timing diagram depicting the ERROR signal and the regulated output voltage as the MIC2951 input is ramped up and down. The ERROR signal becomes valid (low) at about 1.3V input. It goes high at about 5V input (the input voltage at which VOUT = 4.75—for 5.0V applications). Since the MIC2951’s dropout voltage is load-dependent (see curve in Typical Performance Characteristics), the input voltage trip point (about 5V) will vary with the load current. The output voltage trip point does not vary with load. The error comparator has an open-collector output which requires an external pull-up resistor. Depending on system requirements, this resistor may be returned to the output or some other supply voltage. In determining a value for this resistor, note that while the output is rated to sink 200µA, this sink current adds to battery drain in a low battery condition. Suggested values range from 100k to 1MΩ. The resistor is not required if this output is unused.
Programming the Output Voltage (MIC2951) The MIC2951 may be pin-strapped for 5V (or 3.3V or 4.85V) using its internal voltage divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7 (feedback) to Pin 6 (5V Tap). Alternatively, it may be programmed for any output voltage between its 1.235V reference and its 30V maximum rating. An external pair of resistors is required, as shown in Figure 2. The complete equation for the output voltage is VOUT = VREF x { 1 + R1/R2 } + IFB R1 where VREF is the nominal 1.235 reference voltage and IFB is the feedback pin bias current, nominally –20nA. The minimum recommended load current of 1 µA forces an upper limit of 1.2MΩ on the value of R2, if the regulator must work with no load (a condition often found in CMOS in standby), IFB will produce a 2% typical error in VOUT which may be eliminated at room temperature by trimming R1. For better accuracy, choosing R2 = 100k reduces this error to 0.17% while increasing the resistor program current to 12 µA.
Reducing Output Noise In some applications it may be advantageous to reduce the AC noise present at the output. One method is to reduce the regulator bandwidth by increasing the size of the output capacitor. This is the only method by which noise can be reduced on the 3 lead MIC2950 and is relatively inefficient, as increasing the capacitor from 1µF to 220µF only decreases the noise from 430µV to 160µV rms for a 100kHz bandwidth at 5V output.
3-58
February 1999
MIC2950/2951
Micrel
Noise can be reduced fourfold by a bypass capacitor across R1, since it reduces the high frequency gain from 4 to unity. Pick: 1 2 π R1 • 200 Hz
CBYPASS ≅
or about 0.01 µF. When doing this, the output capacitor must be increased to 3.3 µF to maintain stability. These changes reduce the output noise from 430 µV to 100 µV rms for a 100 kHz bandwidth at 5V output. With the bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at higher output voltages.
4.75V
+VIN
OUTPUT VOLTAGE
ERROR
100kΩ
NOT * VALID
5 ERROR
ERROR OUTPUT
NOT * VALID
8 VIN VOUT 1
VOUT = V REF R1 x (1 + ) R2 VOUT 1.2 30V
MIC2951
INPUT VOLTAGE
SHUTDOWN 3 SD INPUT
5V
3.3µF R1 100 pF
OFF
1.3V
GND 4
ON
FB 7
1.23V
* SEE APPLICATIONS INFORMATION
*SEE APPLICATIONS INFORMATION
NOTE: PINS 2 AND 6 ARE LEFT OPEN
Figure 1. ERROR Output Timing
3 R2
V REF
Figure 2. Adjustable Regulator 870 23
Typical Applications
+V IN *SLEEP INPUT 47kΩ
ERROR OUTPUT
+VIN
C-MOS GATE
5
470 kΩ
8 +V IN
ERROR
8 +VIN
SHUTDOWN 3 SD INPUT OFF GND ON 4
FB
5 ERROR
SHUTDOWN INPUT
3
200kΩ + 2N3906 1% 100kΩ 100pF
*VOUT ≈VIN VOUT 1
MIC2951
+V OUT
V OUT 1
MIC2951
ERROR OUTPUT
OFF
3.3µF
ON
SD GND 4
FB 7
7 1% 100kΩ
*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV, DEPENDING ON LOAD CURRENT.
*HIGH INPUT LOWERS VOUT TO 2.5V
Wide Input Voltage Range Current Limiter
5V Regulator with 2.5V Sleep Function
February 1999
3-59
870 25
MIC2950/2951
Micrel +V = 2 → 30V I L↓
5V BUS 1.23V I L= R
LOAD
+V IN VOUT
8 VIN
*V OUT≈5V
MIC2950Z
VOUT 1
+
1µF
MIC2951 SHUTDOWN 3 SD INPUT OFF ON
GND
0.1µF
GND
FB
4
870 27
7 R 1%
5-Volt Current Limiter 1µF
* MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV, DEPENDING ON LOAD CURRENT.
Low Drift Current Source
+V IN
D1
8 +V IN
2 SENSE VOUT
D2
1
MEMORY V+ 20
MIC2951 #1 5 ERROR
1µF
3.6V NICAD
GND 4 27kΩ 870 29
Q1
D3
D4
2.7MΩ
EARLY WARNING RESET
8 +V IN
2 SENSE VOUT
1
MIC2951 #2 5 3 SD ERROR
330kΩ MAIN OUTPUT
+
µP VDO
1µf
GND 4
Regulator with Early Warning and Auxiliary Output • EARLY WARNING FLAG ON LOW INPUT VOLTAGE • MAIN OUTPUT LATCHES OFF AT LOWER INPUT VOLTAGES • BATTERY BACKUP ON AUXILIARY OUTPUT OPERATION: REG. #1’S VOUT IS PROGRAMMED ONE DIODE DROP ABOVE 5 V. ITS ERROR FLAG BECOMES ACTIVE WHEN VIN ≤ 5.7 V. WHEN VIN DROPS BELOW 5.3 V, THE ERROR FLAG OF REG. #2 BECOMES ACTIVE AND VIA Q1 LATCHES THE MAIN OUTPUT OFF. WHEN VIN AGAIN EXCEEDS 5.7 V REG. #1 IS BACK IN REGULATION AND THE EARLY WARNING SIGNAL RISES, UNLATCHING REG. #2 VIA D3.
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February 1999
MIC2950/2951
Micrel +V IN 8 +V IN
470kΩ 5 470kΩ
8
VOUT 1
ERROR
FB
SD
+
RESET
V OUT
1N 4001
R1 7
1µF
4
7
2
FB GND 4
360
* HIGH FOR IL < 3.5mA
1N457
MIN. VOLTAGE
Latch Off When Error Flag Occurs
OUTPUT* 5
1
MIC2951
0.1µF
R2
GND 4
1
V IN
VOUT
MIC2951 3
+5V 4.7mA
20mA
4
4V
Open Circuit Detector for 4mA to 20mA Current Loop
8 +V IN
39kΩ 5
2 SENSE VOUT 1
ERROR
RESET MIC2951 –
3
C4
+
GND 4
39kΩ
+
6V 1% LEADACID BATTERY 1%
100 kΩ
FB
SD
100kΩ
–
C1 <5.8V** 100kΩ
–
C2
+
C1-C4 LP339
1%
1 kΩ
<6.0V** 100kΩ
–
C3
+
R3 1%
7
TAP 6
+
1 kΩ
3
+V OUT = 5V + 1µF
<6.2V**
10kΩ 870 33
20kΩ
C1 TO C4 ARE COMPARATORS (LP339 OR EQUIVALENT) *OPTIONAL LATCH OFF WHEN DROP OUT OCCURS. ADJUST R3 FOR C2 SWITCHING WHEN VIN IS 6.0V **OUTPUTS GO LOW WHEN VIN DROPS BELOW DESIGNATED THRESHOLDS.
Regulator with State-of-Charge Indicator
February 1999
3-61
MIC2950/2951
Micrel +
6V 120kΩ 1.5kΩ** SEALED 1N457 LEADACID BATTERY FB LM385 SOURCE
8 +V IN VOUT 1
– ≈ 400kΩ* FOR 5.5V
MIC2951 3
100kΩ
SENSE
SD
2 1µF
GND 4
* Sets disconnect voltage ** Sets disconnect hysteresis
+
Low-Battery Disconnect For values shown, Regulator shuts down when VIN < 5.5 V and turns on again at 6.0 V. Current drain in disconnected mode is 150µA.
+VIN
8 +VIN 3
AUX. SHUTDOWN INPUT
10kΩ
ERROR
SD
5° PRE-SHUTDOWN FLAG
5
MIC2951
OFF
VOUT 1
ON
GND 4
+
EXTERNAL CIRCUIT PROTECTED FROM OVER TEMPERATURE (V+ GOES OFF WHEN TEMP.> 125°)
FB 7
TEMP. LM34 OR SENSOR LM35 –
OR RELAY
8.2kΩ
LM34 for 125°F Shutdown LM35 for 125°C Shutdown
System Overtemperature Protection Circuit
Schematic Diagram FEEDBACK
IN
R18 20kΩ
Q15A
100 x
Q15B Q24 Q26 Q25
OUT
Q9 Q3
R11 18 kΩ
Q4
Q7
Q6
R11 20.6 kΩ
Q1 10
R2 50 kΩ
Q17
Q16
R27 182 kΩ
R17 12 kΩ
Q14
5V TAP
R28 60 kΩ
Q2 Q20
R1 20 kΩ
Q42
SENSE Q8
Q5
C1 20 pF
R5 180 kΩ
Q40
R6 140 kΩ Q13
Q22
R10 150 kΩ
R8 31.4 kΩ
Q21
R9 27.8 kΩ
R12 110 kΩ
Q12
Q41
Q23
C2 40 pF
R13 100 kΩ
R15 100 kΩ
R14 350 kΩ
R16 30 kΩ
Q11
R17 10 Ω
Q29
R30 30 kΩ
Q18
Q19 Q28
R3 50 kΩ
R4 13 kΩ R21 8 Ω
50 kΩ
Q30 Q31 Q37
10 kΩ
R22 150 kΩ
Q36
SHDN
R24 50 kΩ
R23 60 kΩ
ERROR Q38
Q34 R26 60 kΩ
DENOTES CONNECTION ON MIC2950 ONLY R25 2.8 kΩ
GND
Q39
3-62
February 1999
